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1584 For example. a consistent increase in growing sea~ son base flows will likely alter rhe channel width in some reaches by inundating plant communities and by erosion of fine sediments which provide gtowing mediums fat riparian species. In addi- tion, stream banks may experience catastrophic blow-ours as rhe rivet anempts ro adjust its chan- nel ro the new hydrology. Conversely, consiStently lowet base flows during growing season will allow the encroachment of vegetation inro channel margins. The lower water table associated wirh lower base flows may place water beyond the reach of the root zone of some established plants. The riparian are, may experi- ence a decrease in basal area, density, and width. However, me lower flow may~allow colonization of areas that were previously inundated and could noc support riparian vegeration. Finally, alteration of the annual and seasonal vari- ability in Haws can eliminate processes that are essential ro the survival and evolurion of riparian zones, Petiodic low flow episodes allow plants ro become established in areas whete they willlatet trap and retain sediment. Scouring associated with high flow events creates habitat areas whete early successional plants can become established. b. Reservoirs Maintaining the hisroric panern of opetations at Turquoise Reservoir and Twin Lakes will maintain rhe plant communities which evolved under rhose conditions. Any drawdowns which OCCUt more quickly than rhe historic panern will like!y limit and/or modilY wetland and riparian potential at these reservoirs. Pueblo Reservoit operations do not currently favor wedand and riparian vegetation because of rhe timing and magnitude of drawdowns. Accelerating rhe delivery of water from rhe upper reservoirs to Pueblo in order ro maintain a fuller pool during rhe growing season would be unlikely ro enhance the wetland resource at Pueblo, The quantity of water required to enhance Pueblo Reservoit's tiparian values is much larger than is available for delivery from upper reservoirs. Similarly, maintenance of a poolleve! which enhances riparian/wetland values would tequite operational changes that are presently ourside of the reservoit's operating principles. 3. Water Prefetences For Terresrrial Wtldlife a. Arkansas River The wildlife values associated wirh the Arkansas River corridor and its riparian habitats, wetland habitats, floodplains, and reservoirs are diverse and impOrtant in maintaining rhe ecological Sta- bility of this part of Colorado. Riparian and wet- land areas have been well documented as rhe most productive and amactive of all wildlife habitats. Accordinglv. ripatian areas often provide rhe key resources that support biological diversity both in the riparian and in nearby uplands. Terrestrial wildlife habitat functions provided by the Arkansas River include migtation and dispersal routes, and a to res red connector between habitats for wildlife such as birds, bats, deer, elk and small mammals. In general, flow regimes which support a stable riparian community will also suppOrt the most stJble and diverse assemblage of terrestrial wildlife:. As mentioned in the riparian discussion three fac(Qrs are me most critical in mainrenance of riparian habitats: (1) maintaining the historic frequency and duration of floods, and (2) main- taining growing season groundwater levels in areas adjacent to the stream, and (3) maintaining the annual and seasonal variation in the hydrograph. Petiodic flooding is requited to maintain the species composition of me riparian plant commu- nity because this composition is based upon rhe rolerance of each species ro frequency and dura- cion of Hooding. Flooding is also required ro deposit sediments on which the riparian commu- nity can eStablish, and Hooding provides nutrients for eStablished riparian communities. High flows also provide temporary side channel and backwa- ter habitats that are critical ro some species. The scouting action provided by flooding also pro- vides rhe unvegetated soil and substtates needed in rhe life Stages of some bird and small mammal species. On the other hand, severe flooding of several weeks (sustained flows that are larger and 32